The present invention relates generally to vehicle bodies, and more particularly to a method and apparatus for minimizing asymmetric shedding of vortices on a vehicle forebody.
Aircraft, missiles, and other aeronautical vehicle have high fineness forebodies that are typically solid bodies having solid surfaces. The forebodies at high angles of attack relative to a flowfield tend to shed their nose vortices asymmetrically. By shedding their nose vortices asymmetrically the fluid pressures on a left side and a right side of a forebody are in a non-equilibrium state. The non-equilibrium state generates an undesirable side force and a yaw moment on the forebody, and therefore on the vehicle.
Typically, in order to alleviate the generated undesired side force and yaw rate, stabilizing fins are utilized. The stabilizing fins are attached to the vehicle in a location aft of the center of gravity of the vehicle. The stabilizing fins offset the generated side forces and yaw moments during maneuvering at higher angles of attack. Since, the surfaces of the stabilizing fins are designed for use during high angle of attack flight, the surfaces are over-designed for forces and moments experienced at lower angles of attack, which is unwarranted.
There are also several disadvantages with using stabilizing fins. The stabilizing fins generate more drag on the vehicle, thereby negatively effecting fuel consumption. The stabilizing fins also inherently increase the cost of producing the vehicle due to increase design, material, and production costs. Another disadvantage is that in utilizing stabilizing fins, electrical, pneumatic, or hydraulic control devices are also frequently required to control the stabilizing fins. The control devices increase costs of the vehicle and fuel consumption by increasing the weight of the vehicle.
Similar disadvantages exist for vehicles utilizing various other surfaces similar to that of the stabilizing fins to account for generated undesirable side forces and yaw rates, and also in controlling direction of travel of the vehicle.
Previous forebodies have been designed incorporating a number of porous cavities and interconnected plenums that are controlled and activated by valves and other devices. These forebodies have been found to have little effect on minimizing asymmetric shedding of vortices. Simply adjusting fluid flow through a plenum does not suffice, as performed in traditional forebodies, in equalization of pressures around the exterior of a forebody. The plenums as well as other devices such as transpirational controllers and vacuum pumps add weight to a forebody, thereby, increased fuel consumption and operating costs of a vehicle.
There is a continuous effort to improve the functionality and cost in use and production of an aeronautical vehicle. Therefore, it would be desirable to provide a method and apparatus for minimizing asymmetric shedding of vortices on a vehicle forebody and at the same time decreasing operating and production costs.
The foregoing and other advantages are provided by a method and apparatus for minimizing asymmetric shedding of vortices on a vehicle forebody. A forebody for an aeronautical vehicle is provided. The forebody includes an exterior wall having a first half and a second half. The first half has a first porous section and the second half has a second porous section. The first half and the second half also have a first exterior side experiencing a first fluidic pressure and a second exterior side experiencing a second fluidic pressure, respectively. A hollow inner cavity is fluidically coupled to the first exterior side and the second exterior side and allowing fluid passage between the first exterior side and the second exterior side through the first porous section, the inner cavity, and the second porous section. The exterior wall equalizes the first fluidic pressure with the second fluidic pressure. Additional forebodies and methods for performing the same are also provided.
One of several advantages of the present invention is that it provides an apparatus and method for minimizing asymmetric shedding of vortices on a vehicle forebody, thereby minimizing or eliminating the need for stabilizing fins or surfaces and any accompanying controlling systems. The minimization or elimination of stabilizing fins and corresponding control systems decreases the number of vehicle components and weight of the vehicle, therefore decreasing operating and production costs.
Another advantage of the present invention, depending upon the application, is that it eliminates the need for a solid center surface and plenum within a forebody, which further reduces weight of a vehicle, vehicle complexity, and operating and production costs.
Furthermore, the present invention provides versatility in design and use of a forebody by providing multiple embodiments having various porosity levels, sizes, shapes, materials, forms, and other related features.